The objectives of this study are to develop a new portable rehabilitation device with intelligent control to stretch a ankle joint with spasticity and/or contracture repeatedly to reduce spasticity/contracture in neurologically impaired patients. It will stretch the joint to true extreme plantar- and dorsi-flexion until a specified peak resistance torque is reached with the stretching velocity adjusted constantly based on the resistance torque. Once the peak resistance torque is reached, the ankle will be held at the extreme position for a period of time to let the stress relax before it is rotated back to the other extreme position. The stretching velocity will be very slow at the joint extreme positions, making it possible to reach a larger ROM safely, and it will be fast in the middle ROM so the majority of the stretching exercise is not spent in the middle ROM where contracture/spasticity is less significant. The device will also be used to evaluate outcome in multiple aspects including changes in passive ROM, joint stiffness, viscous damping, energy loss, and reflex gain. Furthermore, functional changes will be evaluated through the active ROM and plantar and dorsi-flexor muscle force-generating capacity. The stretching device will provide a useful tool to both the therapists and neurologically impaired patients. Finally, the stretching device will be low-cost and portable, making it convenient and economical for patients to use in clinic or home and reduce the costs of their treatment. PROPOSED COMMERCIAL APPLICATION: The device can be used to treat spasticity/contracture and evaluate outcome in a number of populations. 1) The device will stretch spastic joints with intelligent control, making it more effective than existing devices. 2) The built-in outcome evaluation will provide quantitative measures of its effectiveness. 3) The low-cost and portable device can potentially be used at home/clinic for convenient treatment, making the potential market large.